Flexible tube structures



Oct. 30, 1962 G. J. SHELDON 3,060,972

FLEXIBLE TUBE STRUCTURES Filed Aug. 22, 1957 3 Sheets-Sheet 1 IO F16. l

INVENTOR.

GILBERT J. SHELDON BY fifl-mak ATTORNEXS Oct. 30, 1962 G. J. SHELDON3,050,972

FLEXIBLE TUBE STRUCTURES Filed Aug. 22, 1957 r 3 SheetsSheet 2 74INVENTOR.

Gl LBERT J. SHELDON ATTORNEYS Oct. 30, 1962 G. J. SHELDON 3,060,972

FLEXIBLE TUBE STRUCTURES Filed'Aug. 22, 1957 s Sheets-Sheet s INVENTOGILBERT J. SHEL N BY M A TTORNE'YS United States Patent Office 3,060,972Patented Oct. 30, 1962 1 3,060,972 FLEXIBLE TUBE STRUCTURES Gilbert J.Sheldon, Irondequoit, N.Y., assignor to Bausch & Lornb Incorporated, acorporation of New York Filed Aug. 22, 1957, Ser. No. 67%,566 Claims.(Cl. 138-120) The present invention relates to flexible tube structuresand particularly to a tube structure the flexing of which may becontrolled both to its extent and in its radius of curvature.

The present invention is particularly adapted for endoscopic deviceswhich heretofore have been restricted in bending in only one directionand to a single extent and radius of curvature. In the use of thepresent day endoscope for viewing the walls of a cavity of the humanbody, it has been necessary to reposition the endoscope a number oftimes into the cavity in order to examine even a portion of the cavitywalls, all at great discomfort to the patient. Since the endoscopescurrently being utilized have restricted flexing capabilities, completeviewing of the walls of the cavity has been impossible.

The flexible tube of the present invention is also capable of beingutilized as a housing for an optical system for other purposes, such as,for viewing remote objects around corners or in other inaccessibleplaces. When suitably encased with a plastic or rubber sheathing, thepresent invention may be adapted for underwater usage wherein movementof the submerged end may be effected by suitable controls located at thedry end. The present invention is also adapted to support a tool at itsworking end so that manipulation of the tool can be accomplished at theremote control end thereof.

In any of its many uses, the flexible tube structure of the presentinvention may be easily disassembled and reassembled if it is desired tolengthen or shorten the structure or to condition the structure for apredetermined radius of curvature. As a housing for any number ofworking tools such as an optical system for endoscopic use, thestructure may be opened up, so to speak, for permitting anymodification, removal or insertion of the optical system or partthereof. Various elements of the tube structure itself may beinterchanged or replaced, added or removed. In its essence, the presenttube structure is composed of various building blocks which may be builtup in various arrangements for a number of purposes.

The primary object of the present invention is to provide a flexibletube structure the flexing of which is adapted to be controlled both asto extent and radii of curvature.

Another object of the invention is to provide a flexible tube structurewhich may be used for supporting working tools and for controllingmanipulation thereof.

Still another object of the invention is to provide a flexible tube forendoscopic devices or other examining instruments which is simple instructure, economical to manufacture and maintain, and capable of beingmodified with a minimum amount of effort.

These and other objects and advantages reside in certain novel featuresof construction, arrangement and combination of parts as willhereinafter be more fully described, pointed out in the appended claimsand will appear when taken in conjunction with the drawing wherein:

FIG. 1 is a side elevational view of one form of the flexible tubestructure constructed in accordance with the invention;

FIG. 2 is a side elevational view of the details of the structure ofFIG. 1, parts being in section for better illustration and showingvarious shapes that the structure may assume;

FIG. 3 is a cross-sectional view taken along line 3-3 of FIG. 2;

FIG. 4 is a fragmentary perspective view of a portion of the tubestructure illustrating the manner in which the structure is assembledand arranged for receiving tools therein;

FIG. 5 is an exploded perspective view of one of the tube sectionsshowing the component parts thereof in greater detail;

FIG. 6 is a side elevational view of another form of the flexible tubestructure;

FIG. 7 is similar to FIG. 6 but illustrates some of the various shapesthe tube structure may assume;

FIG. 8 is a cross-sectional View taken along line 8-43 of FIG. 6;

FIG. 9 is a side elevational view, parts being in section, of anothermodified form of the present invention;

FIG. 10 is an exploded perspective view of the structure shown in FIG.9;

FIGS. 11 and 12 are similar to FIG. 9 but illustrate successive flexingof the tube structure; and

FIG. 13 is a plan view of a modified tube section.

Referring now to the drawings, and more particularly to FIGS. 1-5, thereis shown a flexible tube structure generally indicated by the referencenumeral 10 and comprising a plurality of tube sections 12 arranged in anend to end relationship. As shown in FIGS. 3 and 5, each of the tubesections 12 is composed of two identical semi-circular elements 14, 16,each of which is formed with a pair of axially spaced connecting lugs 18at one end and a single lug 20 at the other end. When the elements 14,16 are joined together to form a single tube section, the lug 20 of eachof the elements is retained between the two lugs 18 of the otherelement. The lugs 18 and 20 are suitably shaped so that when theelements are joined, the outer surface of the tube section 12 isunbroken and conforms with the surrounding circular surface. As shown inFIGS. 2 and 3, the lugs 18 and 20, when interlocked, form continuoustransverse thickened portions or ridges which extend radially inwardlyslightly from the circumference of the tube section and arediametrically opposed.

A similar pair of ridges 22 are formed on the inner wall surfaces of thetube sections and these are arranged in diametrically opposed positionsat about a displacement from the ridges formed by the lugs 18 and 20.Each of the ridges is formed with openings which in the presentembodiment are in the form of apertures 24, 26, respectively, and in thecase of the lugs 18 and 20, the apertures 24 extend in axial alignmentwhen the elements 14, 16 are joined together, as shown in FIGS. 1 and 2.

The apertures 24 in each of the tube sections are adapted to accommodatea flexible cable 28 which extends through the length of the tubestructure 10. Similarly, the apertures 26 are adapted to accommodateanother flexible cable 30. It will be apparent that when the tubesections 12 are arranged in axial alignment as shown in FIG. 1, theapertures 24 of each of the tube sections are in axial alignment withthe corresponding apertures in the preceding tube section and theapertures 26 of each of the tube sections are in axial alignment withthe corresponding apertures in the preceding tube section.

One end of each of the cables 28, 30 may be directly secured to theterminal tube section 32 or connected indirectly thereto by means ofsuitable sleeves 34 which are made small enough to be swaged upon theends of the cables and may be suitably welded to the section 32. Theother ends of the cables 28 are similarly encircled by sleeves 36 withthe ends swaged thereto. A coil spring 38 encircles each of the cables28 and is held in com- 3 pression between the sleeve 36 and the adjacenttube section. The cables 30 may be connected together and held tautaround a suitable control pulley, this structure being shown in FIG. 7and will be described hereinafter.

A plurality of spacer annular elements 40 which may be in the form ofwashers or sleeves are positioned on the cables between some of the tubesections and for purposes of this invention, such washers or sleeves areutilized in that portion of the tube structure where flexing thereof isdesired. As shown in FIG. 1, the flexed portion of the tube structure 10is provided with these annular elements. To complete the structure ofthe embodiment of FIG. 1, the entire structure 10 may be suitablecovered with a rubber or plastic sheathing 42 which would provide asmooth and continuous finish for the structure and perm-it the use ofthe structure in water or other moist surrounding without aifecting theelements of the structure.

In operation, a pulling force exerted upon one of the cables 30 willproduce flexing of the terminal portion of the tube structure, or thatend illustrated in the righthand portion of the structure of FIG. 1. Theamount or extent of flexing is controlled by the amount of force exertedupon the cable 30 and it is possible to flex this end of the structureuntil the same assumes substantially the shape of a complete circle. Adesired radius of ourvature or any change thereof is determined by theaxial length of the annular elements 40, and in the case of washers,this would be determined by the thickness thereof, and in the case ofsleeves, by their length. If a large radius of curvature is desired,washers or sleeves having short lengths should be utilized, and in theevent a sharp flexing, or one having a small radius, is desired, sleeveshaving relatively long lengths should be utilized. This relationship isillustrated in FIG. 2 wherein use of the large sleeves 44 has permitteda sharp flexing of the tube structure and small sleeves 46 havepermitted only a slight flexing. Any other desired shape of the flexedportion of the tube structure may be planned by simply using varioussizes of spacer washers or sleeves.

Radii of curvature may also be varied by utilizing tube sections havingother axial dimensions. In the embodiment of FIGS. 1-5, the tubesections are relatively wide, that is, their axial dimensions are longwhen compared to the embodiments shown in FIGS. 6-l3. In FIG. 2, if thetube sections were replaced by ones having a smaller width, or in fact,by a tube section which is in the form of a plate, the flexing wouldeven be sharper if the same number of tube sections are used. On theother hand, if a greater number of these plates or narrow tube sectionsare used, the radii of curvature are progressively increased. Therefore,the width of the tube sections, whether they be in the form plates or asize similar to that shown in FIG. 2, or the number of these tubesections utilized, will each contribute to the control of the raddi ofcurvature.

For purposes of further description the cables 30 are considered ascontrol cables while the cables 28 are to be treated as tying cables. Apulling force exerted on either of the control cables 30 will flex thecable :in the plane defined by both the cables 34) and, the cables 28will retain the tube sections to maintain the length of the tubestructure 10, along its axis, which during flexing will assume the formexperienced by the cables 28, substantially constant. During a flexingoperation, the coil springs 38 serve as override mechanism and to assistin maintaining the length of the tube structure, along its axis,substantially constant. If the spacers 40 were perfectly rounded attheir ends and of a predetermined radii of curvature, there would be nonecessity for the coil springs 38 since, no matter what shape or formthe tube structure assumes, its axial length would never vary and theanchor sleeves 34, 36 for the cables 28 would be suflicient formaintaining the length of the tube structure constant. However, sincethere is no need in the present invention for perfectly machined parts,the coil springs 38 cooperate with the anchor sleeve 36 to permit slightchanges in the length of the tube structure if the occasion arises. Anychange in length will be extremely small and will be caused solely bythe inaccuracies of the various elements of the tube structureespecially in the spacers 40. Thus, the tube sections are constantlyheld together during flexed or non-flexed conditions of the tubestructure and the constant length of the tube structure may beattributed to the anchor sleeves 36 which are swaged to the ends of thecables 28 or to the use of the coil spring 38 in conjunction with thesleeve 36.

It will be apparent that the tube structure 10 is capable of moving theterminal section 32 in a relatively wide arc with the radius ofcurvature thereof struck from a point between the last tube sectionwhich does not flex and the adjacent tube section which does flex, suchpoint being illustrated in FIG. 1, at 48. For endoscopic use, thischaracteristic has the particular advantage in that different parts of acavity under inspection may be viewed without the necessity of continualwithdrawal of the tube structure and rotation thereof during inspection.

Another advantage of the present invention is the simplicity of assemblyand the arranging of worktools within the tube structure. In FIG. 4, aportion of the tube structure is illustrated with one of the tyingcables 28 removed and the individual tube sections opened up, so tospeak. To accomplish this, one of the cables. 28 is disengaged from itsanchor sleeve 34 and pulled through the lugs 18, 20, whereupon one ofthe elements 14, 16 in each tube section is pivoted about the remainingtying cable 28. With all of the tube sections in this position, anydesired optical system or other equipment may be installed, modified orreplaced in the interior of the tube structure.

The present invention is also adapted to serve as a flexible controllinkage for a tool which may be conveniently mounted at the terminaltube section 32 thereof. In an arrangement of this sort, the tubestructure 10 would serve as a remote control linkage for the tool andwould provide a flexible housing for any electrical wires, hoses,flexible shafts, etc. for the tool.

The embodiment of FIGS. 6-8 is similar to that of FIGS. 1-5 and differstherefrom only in compounding the various functions of the latter. Thetube structure comprises tube sections 50, 52 which for purposes ofillustration, are shorter in axial length than the sections shown inFIG. 1. The upper portion 54 of the tube structure includes the tubesections 50 of the same structure as the tube section illustrated inFIG. 3, however, the lower portion 56 includes the tube sections 52having a structure of the cross-section as .shown in FIG. 8.

Each of the sections 52 is provided with two pairs of diametricallyopposed apertures 58, 60 which are similar to apertures 24, 26,respectively, shown in FIG. 3. The tube sections 52 also include anotherpair of apertures 62 which are diametrically opposed with respect toeach other but in close adjacency with the apertures 60. The sections50, 52 also include the interlocking lugs which are provided on the tubesections 12 thus permitting easy assembly and opening up of the tubestructure of FIG. 6.

A pair of tying cables 64- is threaded through the pairs of apertures58, respectively, with one end of each of the cables secured to aterminal tube section of the upper portion 54 and the other ends swagedor otherwise secured to sleeves 66. coil springs 68 are held incompression between the sleeves 66 and the adjacent tube section 70 andserve the same purpose as does the spring 38 in the embodiment ofFIG. 1. As in the previous embodiment, annular elements 72 in the formof spacer washers or sleeves are provided between some of the tubesections for both upper and lowe portions 54, 56, depending, aspreviously described, on the amount of flexing desired. In FIGS. 6 and7, it will be noted that the lengths of the sleeves for the upperportion are greater than those of the lower section.

A pair of control cables 74 are threaded through the apertures 60,respectively, in the lower portion 56 and the ends of these cables aresecured at 76 to the tube section 78 which is the terminal section forthe portion 56. Another pair of control cables 80 are threaded throughthe apertures 62 and then extended through both portions 54, 56 of thetube structure. In FIG. 7, the terminal ends of the cables 80 aresecured at 82 to the terminal section 84 of the portion 54.

The other ends of the cables 80 remote from its ter minal ends arejoined together and looped around a pulley 86 which is suitablyconnected to a control knob 88 by a shaft 90. Similarly, the ends of thecontrol cables 74 remote from its terminal ends are joined together andlooped around a pulley 92. A suitable knob 94 is rigidly connected tothe pulley 92 for imparting rotation thereto.

In operation, rotation of the knob 88 in either direction willcorrespondingly impart a pulling force to one of the cables 80 andrelease, correspondingly, tension in the other cable. Such a pullingforce will flex the upper portion 54 while the lower portion 56 remainsstraight. it it is desired to extend the terminal end of the tubestructure at different radii of curvature, the knob 94 may be rotated inthe same direction as the rotation of the knob 88, as shown in FIG. 7.The apparatus may assume other shape or conditions of flexing dependingupon the extent and manner desired. For example, from the conditionshown in FIG. 7, the knob 88 may be rotated in order to straighten theupper portion 56 resulting in two straight sections separated by aflexed portion. The knob 88 may be rotated in the complete oppositeextreme so that the upper portion is curved oppositely to that shown. Inthis case, the tube structure would assume an S-shape.

In the embodiment of FIGS. 9-13, the tube sections 100 are shown to bethin plate-like units as compared to the tube sections in the previousembodiments. It will be understood that this diflerence is merely forillustration purposes and that the tube sections for all of theembodiments may be of any desired length. Similarly, the tube sections100 may be composed of two interlocking semi-circular ring elements,such as shown in FIG. 5. The advantage of the thin type of section isthat in the use of a great number of the sections for a relatively shortradius of curvature, the flexed tube structure will assume a moreperfect smoothly curved structure rather than a many-sdided arc whichresults when the tube sections are long, such as shown in FIG. 1.

Each of the tube sections 100 is formed with a pair of opposed openings102 in the form of round apertures and a pair of opposed openings 104 inthe form of slots. The apertures 102 receive a pair of control cables106, respectively, and these may be suitably anchored on the terminaltube section (not shown). The other ends of the cables 106 may beconnected together and arranged around a pulley in much the same fashionas in the previous embodiment.

The present embodiment differs from the previously described embodimentsin the use of flexure strips, preferably of spring material, instead oftying cables and coil springs 38, 68. A pair of resilient flexure strips108 having spaced notches or cut-outs 110 and spacer portions 112therebetween is adapated to be received in the openings 104,respectively. To provide the tube struc ture with flush external andinterior surfaces, the width of the strips 108 is made equal to thewidth of the tube sections and the depth of the openings 104 made equalto the portion of the strips above the notches 110 which in turn willreceive the portion of the tube sections below the openings 104. Theentire tube structure shown in FIGS. 9l2 may be encased in a rubber orplastic jacket or sheathing 114 which serves to maintain the flexurestrips 108 in proper relationship with respect to the tube sections. Itwill be appreciated that the present embodiment is rather easy toassemble or disassemble, requiring only the holding of the tube sectionsand the insertion or removal of the strips 103 from their respectivepositions. The unique advantage in using a spring flexure strip insteadof cables is that twisting of the tube structure is minimized oreliminated in the event that a relatively heavy tool is associatedtherewith either internally or mounted at the end.

The amount of flexing of the tube structure shown in FIGS. 912, dependsupon the length of the spacer portions 112 and/ or the length of thetube sections 100, such requirements being determinative for thevariance of flexing in the embodiments of FIGS. 1 and 6. If longer tubesections are to be utilized, the notches would be correspondinglylonger. In FIGS. 11 and 12 there is shown, in step sequence, theprogress of flexing when a force is exerted upon one of the cables 106.This progress would hold true for all of the embodiments of theinvention. The force would initially flex the flexure strip portionsbetween the two end tube sections until one end of the terminal tubesection abuts the first succeeding section whereupon the continuingforce will flex the flexure strip portions between the first succeedingsection and the next succeeding section, and so on, until the desiredamount of curvature is attained.

By having the notches 110 interlockingly engaged with a correspondingslot, the tube sections are held from displacement along the axis of thetube structure. Consequently, this engagement erves to retain the tubesections to maintain the length of the tube structure along its axissubstantially constant. If a permanent arrangement is desired, a notchedflexure strip may be dispensed with and one having continuous edgescould be threaded through the slots 104. A weld may then be applied toevery juncture of the strip with a tube section.

In FIG. 13, there is shown an oval tube section having thickenedportions on two sides thereof which may be substituted for the circulartube sections of the structure shown in FIG. 9. The advantage in the useof the oval tube section when the tying flexible element, whether it bea cable or flexible strip, is associated with the ends of the sectionhaving the greater diameter, is that there is less tendency for the tubestructure to twist while being flexed, which may occur if the tyingflexible elements are not sufficiently taut or the parts are looselyfitted. This has particular advantage for a device similar to thestructure shown in FIG. 6 wherein there is a tendency for the structureto twist when a force is exerted on the cables 80. The twisting herewould be occasioned because of the ofl center location of the openings62 for the cables 80. Since one of the openings 62 is closer to one ofthe openings 58, a torque will be developed tending to twist thestructure when the cable is pulled. In the use of an oval tube section,the tying flexible element has a greater moment arm, that is, thedistance between the element and the axial center of the tube section,than the moment arm for the control cable. Therefore, the cable may belocated off-center somewhat and its use thereof will not affect thealignment of the tube structure.

From the foregoing description, it will be appreciated that the presentinvention provides a flexible tube structure which may be flexed in acontrolled manner, both as to extent and as to its radii of curvature.The flexible tube structure may be easily disassembled and reassembled,may be shortened or lengthened and may serve as a housing or a flexiblesupport for various tools. While only specific assemblies areillustrated and described, it will be understood that this is forbrevity only and that various other arrangements may be utilized. Forexample, the embodiment of FIG. 6 may be compounded into any number ofindividual flexing portions requiring only the addition of more openingsand control cables for the additional portions. It will be understoodthat all of the tube sections in any of the embodiments may be oval incross-section. While not illustrated, the tube sections for any of theembodiments may include many openings in order to accommodate controlwires, or cables for tools, housed within the tube structure or at theend thereof. These openings as well as those for the various flexibleelements described may be made in thickened protruding portions of thetube sections such as those shown in FIGS. 3 and 8 or in the walls ofthe tube sections such as shown in FIG. 13. These and many moremodifications and arrangements of the present invention may be made oremployed without departing from the spirit or scope of the appendedclaims.

I claim:

1. A flexible tubular structure comprising, a plurality of tubularsections arranged in end-to-end relationship, spacer means defininglongitudinal openings positioned diametrically opposed to each other andpivotally positioning said tubular sections relative to each other, aplurality of openings in said tubular sections each of which is alignedwith corresponding openings on the preceding tubular section to form atleast two pairs of aligned openings extending longitudinally of thetubular structure, a first pair of cables extending through one of saidpairs of openings, a second pair of cables extending longitudinallythrough the second pair of openings in said tubular sections and thelongitudinal openings in said spacer means, means securing one of theends of each of said first pair of cables to the tubular sectionadjacent to the ends or" said cables, means securing the other ends ofeach of said first pair of cables and one end of each of said secondpair of cables tothe tubular section adjacent said other ends of saidfirst pair of cables, whereby a pulling force exerted upon either cableof said second pair of cables will produce a flexing of the tubularstructure.

2. A flexible tubular structure comprising, a plurality of tubularsections arranged in end-to-end relationship, spacer means positioneddiametrically opposed relative to each other and pivotally positioningsaid tubular sections in spaced relation to each other, each of saidtubular sections consisting of two semi-circular ring elementsinterlockingly connected at their respective ends, a plurality ofopenings formed in said tubular sections each of which is aligned withthe corresponding openings of the preceding tubular section to form atleast four series of aligned openings extending longitudinally of saidtubular structure, two of said series of openings extending throughconnecting ends of said ring elements, said spacers positioned betweenadjacent ends of said tubular sections one at each of the connectingends of the tubular sections in axial alignment with openingstherethrough, a first pair of cable strung through the series ofopenings which extend through the interconnecting ends of the ringelements, and the spacers associated therewith, a second pair of cablesstrung through the second of said series of two aligned openings, meanssecuring the first ends of each of said first pairs of cables to thetubular section adjacent said ends, means securing the second ends ofeach of said first pair of cables to the tubular section adjacent saidother end of said first pair of cables, means securing the first ends ofsaid second pair of cables to thereby permit flexing of the tubularstructure upon exerting a pulling force upon one of said second pair ofcables.

3. A flexible tubular structure comprising, a plurality of tubularsections arranged in end-to-end relationship, a plurality of spacerelements diametrically disposed to pivotally position said tubularsections in spaced relation, a plurality of openings in said tubularsections axially aligned with the corresponding openings of thepreceding tubular section to form at least four series of alignedopenings extending longitudinally of the tubular sections, a pluralityof openings extending longitudinally through said spacer elements, saidspacers positioned between the adjacent ends of said tubular sections inaxial alignment with a pair of the openings therein, a first pair ofcables strung through the series of openings which extend through saidspacers associated therewith, a second pair of cables strung through thesecond two of said series of aligned openings, means securing the commonends of said cables to the section adjacent the ends of said cables,means tensioning the opposite ends of said cable extending through saidspacers, thereby permitting a pulling force exterted upon either side ofsaid second pair of cables to produce a flexing of the tubularstructure.

4. A flexible tubular structure comprising, a plurality of tubularsections arranged in end-to-end relationship, a plurality of angularlyspaced axial passages in said tubular sections each of said passagesaxially aligned with corresponding passages of adjacent tubular sectionsto form at least two pairs of aligned openings extending longitudinallyof the tubular structure, two spacers positioned between adjacent endsof said tubular sections to pivotally position said tubular sections inspaced relation relative to each other, an arcuate surface on theengaging ends of said spacers to permit said tubular sections to roll onthe arcuate surface of said spacers when said tubular sections areflexed relative to each other, a first pair of flexible elementsextending through one of said pairs of openings and said spacersassociated therewith for tensioning said tubular sections, a second pairof flexible elements extending through a second pair of openings in saidtubular sections, means securing one of the ends of said second pair offlexible elements to the adjacent tubular section whereby a pullingforce exerted on one of said second pair of flexible elements willproduce a flexing of the tubular structure.

5. A flexible tubular structure comprising, a plurality of tubularsections arranged in end-to-end relationship, a plurality of openingsextending longitudinally through each of said tubular sections each ofwhich is aligned with the corresponding opening of the adjacent tubularsection to form at least two pairs of aligned openings extendinglongitudinally of the tubular structure each of said pairs beingdiametrically opposed, a first pair of flexible elements extendingthrough said firs-t pair of openings, a second pair of flexible elementsextending through the second pair of axially aligned openings, spacermeans positioned between adjacent ends of successive tubular sectionsand arranged in the plane defined by said first pair of flexibleelements, said spacers pivotally positioning adjacent tubular sectionsrelative to each other, means preventing movement of the portions ofsaid flexible elements adjacent the end tubular section of the tubularstructure, means preventing movement of the portions of said first pairof flexible elements adjacent to the end tubular section relative tosaid first end section whereby a pulling force exerted on either of saidfirst pair of elements will produce a flexing of the tubular structureabout the spacer elements.

References Cited in the file of this patent UNITED STATES PATENTS731,496 Pairier et al. June 23, 1903 944,830 Sussman Dec. 28, 19081,044,044 Hardesty Nov. 12, 1912 1,482,576 Myers Feb. 5, 1924 2,241,576-Barton May 13, 1941 2,498,692 Mains Feb. 28, 1950 2,540,141 Shafer Feb.6, 1951 2,799,274 Eisenhut July 16, 1957 2,975,785 Sheldon Mar. 21, 1961FOREIGN PATENTS 179,905 Austria Oct. 25, 1954 339,757 France Apr. 26,1904 UNITED STATES PATENT. OFFICE CERTIFICATE OF CORRECTION Patent No.3,060,972 October 30, 1962 Gilbert J. Sheldon It is hereby certifiedthat error appears in the above numbered patent requiring correction andthat the said Letters Patent should read as corrected below.

Column 1, line 15, for "of", second occurrence, read in column 13,- line13 for "suitable" read suitably line 49, for "plates" read plate line52, after "form" insert of line 55, for "raddi" read radii column 5,line 48, for many--sdided" read many-sided line 64', for "adapated" readadapted column 7, line 53, for "cable" read cables Signed and sealedthis 23rd day of April 1963.

(SEAL) Attest:

ERNEST w. SWIDER DAVID LADD. Attesting Officer Commissioner of PatentsUNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent Non3,060,972 October 30, 1962 Gilbert J. Sheldon It is hereby certifiedthat error appears in the above numbered patent requiring correction andthat the said Letters Patent should read as corrected below.

Column 1, line 15, for "of",second occurrence, read in column 3, line 13for "suitable read suitably line 49 for "plates" read plate line 52,after "form" insert of line 55, for "raddi" read radii column 5, line48, for "many-sdided" read manysided line 64, for "adapated" readadapted column 7, line 53, for "cable" read cables Signed and sealedthis 23rd day of April 1963.

(SEAL) littest:

ERNEST w. SWIDER DAVID LADD Attesting Officer Commissioner of Patents

